The present invention relates, in general, to ultrasonic surgical clamping instruments and, more particularly, to an improved force limiting mechanism for an ultrasonic surgical clamping instrument.
This application is related to the following copending patent application: Application Ser. No. 08/948,625 filed Oct. 10, 1997; Application Ser. No. 08/949,133 filed Oct. 10, 1997; Application Ser. No. 09/106,686 filed Jun. 29, 1998; Application Ser. No. 09/337,077 filed Jun. 21, 1999; Application Ser. No. 09/412,557 filed Oct. 5, 1999; Application Ser. No. 09/412,257 filed Oct. 5, 1999; Application Ser. No. 09/413,225 filed Oct. 5, 1999, which are incorporated herein by reference.
Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end-effector, may be used to cut, dissect, or cauterize tissue. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer through the waveguide to the surgical end-effector. Such instruments are particularly suited for use in minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end-effector is passed through a trocar to reach the surgical site.
Ultrasonic vibration is induced in the surgical end-effector by, for example, electrically exciting a transducer which may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument hand piece. Vibrations generated by the transducer section are transmitted to the surgical end-effector via an ultrasonic waveguide extending from the transducer section to the surgical end-effector.
Solid core ultrasonic surgical instruments may be divided into two types, single element end-effector devices and multiple-element end-effector. Single element end-effector devices include instruments such as scalpels, and ball coagulators, see, for example, U.S. Pat. No. 5,263,957. While such instruments as disclosed in U.S. Pat. No. 5,263,957 have been found eminently satisfactory, there are limitations with respect to their use, as well as the use of other ultrasonic surgical instruments. For example, single-element end-effector instruments have limited ability to apply blade-to-tissue pressure when the tissue is soft and loosely supported. Substantial pressure is necessary to effectively couple ultrasonic energy to the tissue. This inability to grasp the tissue results in a further inability to fully coapt tissue surfaces while applying ultrasonic energy, leading to less-than-desired hemostasis and tissue joining.
The use of multiple-element end-effectors such as clamping coagulators include a mechanism to press tissue against an ultrasonic blade, that can overcome these deficiencies. A clamp mechanism disclosed as useful in an ultrasonic surgical device has been described in U.S. Pat. Nos. 3,636,943 and 3,862,630 to Balamuth. Generally, however, the Balamuth device, as disclosed in those patents, does not coagulate and cut sufficiently fast, and lacks versatility in that it cannot be used to cut/coaglulate without the clamp because access to the blade is blocked by the clamp.
Ultrasonic clamp coagulators such as, for example, those disclosed in U.S. Pat. Nos. 5,322,055 and 5,893,835 provide an improved ultrasonic surgical instrument for cutting/coagulating tissue, particularly loose and unsupported tissue, wherein the ultrasonic blade is employed in conjunction with a clamp for applying a compressive or biasing force to the tissue, whereby faster coagulation and cutting of the tissue, with less attenuation of blade motion, are achieved. However, for optimal tissue coagulation and cutting speed it is desirable to prevent application of excessive clamping force, while providing good tactile feedback to the instrument""s user. A force limiting clamping mechanism has been described in U.S. patent application Ser. No. 08/949,133 filed Oct. 10, 1997, and previously incorporated herein by reference.
Improvements in technology of curved ultrasonic instruments such as described in U.S. patent application Ser. No. 09/106,686 previously incorporated herein by reference, have created needs for improvements in other aspects of curved clamp coagulators. For example, U.S. Pat. No. 5,873,873 describes an ultrasonic clamp coagulating instrument having an end-effector including a clamp arm comprising a tissue pad. In the configuration shown in U.S. Pat. No. 5,873,873 the clamp arm and tissue pad are straight.
Although the force limiting mechanism described in U.S. patent application Ser. No. 08/949,133 has proven eminently successful, it would be advantageous to provide an improved force limiting feature on an ultrasonic surgical instrument. It would be advantageous for the improved force limiting mechanism to be small and easily incorporated into the instrument, to facilitate small ergonomic instrument designs with ease of manufacturing and a robust design.
An improved force limiting feature is described for use with an ultrasonic surgical instrument. An ultrasonic clamp coagulator apparatus is described including a housing, an actuator, an outer tube having a proximal end joined to the housing, and a distal end. An actuating element is reciprocably positioned within the outer tube and operatively connected to the actuator. An ultrasonic waveguide is positioned within the outer tube, with an end-effector extending distally from the distal end of the outer tube. A clamp arm is pivotally mounted on the distal end of the outer tube for pivotal movement with respect to the end-effector for clamping tissue between the clamp arm and the end-effector. The clamp arm is operatively connected to the actuating element so that reciprocal movement of the actuating element pivots the clamp arm. There is an actuation mechanism within the housing, connected between the clamp arm and the actuator. The actuation mechanism is adapted to actuate the clamp arm pivotably with respect to the end-effector. In one embodiment the actuation mechanism includes a wave spring for limiting the force applied to the clamp arm from the actuator.